1. Field of the Invention
The invention relates to optical readers in general, and in particular to a method for operating a portable trigger-actuated optical reader in a way that enables the reader to accurately and rapidly read symbols in scenes having multiple symbols.
2. Background of the Prior Art
Currently available portable trigger-activated optical readers are typically configured to operate in "repeat until done" mode. A reader configured in this operating mode will continuously capture frames of image data in response to a trigger being pulled, and will attempt to decode any symbol which may be represented in that image data. The reader will continuously scan and attempt to decode image data until a first symbol is successfully decoded. When a first symbol is successfully decoded, the reader automatically stops capturing image data and stops attempting to decode image data. The trigger of the reader must be pulled again if a user wishes to decode a second symbol.
The repeat-until-done operating protocol is highly useful in the case where the reader is used to decode an isolated symbol that is formed in a region a substantial distance away from other symbols. The operating method prevents unnecessary re-decoding of the same symbol, and redundant outputting of identical data messages during the time a trigger is pulled.
However, in recent years, it has become increasingly common to form multiple bar code symbol in close proximity to one another on packages and other objects. A user operating a reader configured in a repeat-until-done mode will frequently encounter difficulty in attempting to decode symbols in scenes having more than one symbol and in particular scenes having multiple symbols formed in close proximity to one another. In order to capture and decode two symbols using a reader configured in a repeat-until-done mode, it is necessary to pull the trigger to decode a first symbol, release the trigger, and then pull the trigger again in order to attempt to decode the second symbol. In addition to being cumbersome and time consuming, there is no assurance that the method will be effective in decoding and outputting message data from both symbols, particularly if the two symbols are closely spaced. During the period in which the trigger is pulled for the second time, the reader may decode a first symbol that was decoded when the trigger was pulled for the first time, without decoding the second symbol.
There is a need for a method for operating an optical reader so that the reader accurately and rapidly decodes symbols in scenes having multiple symbols, and particularly symbols formed in close spaced relation to one another.